This is chapter No 1 of Pharmaceutical Chemistry - I for Diploma in Pharmacy (D. Pharmacy) Details notes for Diploma in Pharmacy (D.Pharmacy) Students.

1. ACIDS , BASES ,
BUFFERS (5-6 M)
BY
CHETAN V. JAIN
(M.PHARMACY PHARMACEUTICS)
CHAPTER 1

2. Acids, Bases are defined by
Four main theories
1. Traditional theory / concept
2. Arrhenius theory
3. Bronsted and Lowry theory
4. Lewis theory

3. 1. Traditional theory / concept
 Acid : are the substance
 Which converts blue litmus paper to red
 Having the PH < 7
 Sour Taste
 React with bases to form salts and Water
 Eg :- Hydrochloric acid (HCl)

4.  Base : are the substance
 which converts red litmus paper to blue
 Having the PH >7
 Bitter taste
 React with Acids to form salts and water
 Eg: Sodium Hydroxide (NaOH)

5. 2. Arrhenius theory*
 In 1884 of Svante Arrhenius Also
known as, Arrhenius theory of
ionization
 Electron dissociation theory
 This theory define acids & bases
according to there formation of ions
when dissolved in water

6. Arrhenius theory : Acid
 An Acid is a substance that can
release hydrogen ion (H+) when
dissolved in water or A substance
which when dissolved in water gives
hydrogen ions (H+) is known as acid
 Hydrochloric acid (HCl)

7. Arrhenius theory : Base
 A Base is a substance that can
release a Hydroxyl ion (OH-) when
dissolved in water Or A substance
which when dissolved in water gives
Hydroxyl ion (OH-)is known as Base
 Eg : Sodium Hydroxide [NaOH]

8. Neutralization reaction
 Acids react with Base and form Salt
& Water
 Eg: Hydrochloric acid react sodium
hydroxide and form Sodium chloride
(Salt) & water
NaOH + HCl = NaCl + H2O
( BASE) + (ACID) = (SALT) + (WATER)

9. Limitation of Arrhenius theory
 Water is essential
 Not explain Acidity or Basisity of non
aqueous Solvent Eg :Benzene
 Basisity of Ammonia (No OH- ion) is
not explained
 Acidity of BF3,AlCl3 (No H+ ion) is not
explained

10. 3. Bronsted and Lowry theory
 Bronsted in Copenhagen and Lowry in
London independently in 1923
proposed simultaneously new definition
of acid and base
 Acid : is a substance that can donate a
proton i.e. acid is a proton donor.
 Base : is a substance that can accept a
proton i.e. base is a proton acceptor.

11. Bronsted and Lowry theory

12. 4. Lewis theory
 One of the simplest bonding theories
was developed by G.N. Lewis and is
called Lewis Theory.
 Acid : is a molecule or ion that can
accept a lone pair of electrons.
 Base : is a molecule or ion that has a
lone pair of electrons whish is
donated.

13. Lewis theory

14. Strong & Weak Acid and Base
 Strong Acid : Produce more amount of
H+ ions in water. E.g. HCl
 Weak Acid : Produce less amount of H+
ions in water. E.g. CH3COOH
 Strong Base : Produce more amount of
OH- ions in water. E.g. NaOH
 Weak Base: Produce less amount of
OH- ions in water. E.g. NH4OH

15. Strong & Weak Acids and Bases
Acids Bases
Strong Weak Strong Weak
HCl CH3COOH NAOH NH4OH
H2SO4 HCN KOH NaHCO3
NHO3 C6H5COOH CaO C6H5NH2
HCIO4 HCOOH Na2CO3 CH3NH2
HCIO3 H2CO3 - -
HBr C6H5OH - -
HI - - -

16. Buffer Solution
 It is capable to resist / appose / prevent
the change in pH or pOH value when
adding in small amount of acid & base.
 Types of Buffer Solutions
1. Acidic Buffer : solution contains weak
acid and salt known as acidic buffer.
2. Basic Buffer : solution contains weak
base and salt known as basic buffer.

17. pH and pOH
 pH : - log
 pOH : - log
 Therefore pH + pOH = 14
7 + 7 = 14
H+
10
OH-
10

18. Some Official Acids & Bases
 Acids
 Boric Acid [H3BO3]
 Hydrochloric Acid [HCl] Conc. & Dil
 Bases
 Strong Ammonium Hydroxide [NH4OH]
 Calcium Hydroxide [Ca(CH)2]
 Sodium Hydroxide [NaOH]

19. Official Acids

20. Boric Acid [H3BO3]
 Synonym- Boracic Acid , Orthoboric Acid,
 Limit: It contains not less than 99% & not
more than 100.5% of H3BO3
 Preparation :- Borax with Sulphuric acid in
presence of water
Na2B4O7 + H2SO4 + 5H2O = 4H3BO3 + Na2SO4

21. Boric Acid [H3BO3]….
 Physical Properties:
 White crystalline powder
 Odorless
 Insoluble in water
 Soluble in Ethanol
 Soluble in glycerin

22. Boric Acid [H3BO3]….
 Uses :
 Local anti-infective
 To maintain acidic pH medium in
Medicament
 Preparation of buffer solution
 In ophthalmic preparation
 Dusting powder
 Preparation of ointment

23. Conc. Hydrochloric Acid [HCl]
 Synonym : Muriatic Acid
 Limit : Not less than 35% and not
more than 38% of HCl
 Preparation : Conc Sulfuric acid react
with sodium chloride
NaCl + H2SO4 = HCl + NaHSO4

24. Conc. Hydrochloric Acid [HCl]…
 Physical Properties
 Clear Colorless Liquid.
 Pungent Odor.
 Miscible with water and alcohol.
 Fuming liquid.

25. Conc. Hydrochloric Acid [HCl]…
 Uses :
 As a Pharmaceucal Aid (Acidifying Agent)
 As a solvent in Industry
 As a reagent in Laboratory
 For manufacturing of basic Pharmaceuticals.
 Storage : temp not exceeding 30 C in a
glass stopped container.

26. Dil. Hydrochloric Acid [HCl]
 Synonym, Limit, Properties, uses and
Storage same as Conc. Hydrochloric
Acid [HCl]
 Preparation : 10 ml Conc. HCl + up
to 100 ml Water

27. Official Bases

28. Strong Ammonium Hydroxide
[NH4OH]
 Synonym : Ammonium hydroxide, strong
ammonium water, liquor ammoniae forties
 Limit : Not less than 25% of ammonia
 Preparation : By mixing ammonium
chloride with slaked lime
NH4Cl + Ca(OH)2 =NH4OH + CaCl2

29. Strong Ammonium Hydroxide
[NH4OH]….
 Physical Properties
 Clear colorless liquid
 Pungent odor
 Characteristic taste
 Miscible with water
 Aqueous solution is
strongly
 Alkaline in nature
 Uses
 Alkalizing agent
 Reflux stimulant
(fainted person)
 Vasoconstrictor
 Strong base
 Antacid
 Reagent in Laboratory
 Storage : store in umber color bottle with rubber stopper

30. Calcium Hydroxide [Ca(CH)2]
 Synonym: Slaked Lime, Lime
water
 Preparation:- By treating calcium
chloride with sodium hydroxide
CaCl2 + 2NaOH = Ca(OH)2 + 2NaCl

31. Calcium Hydroxide [Ca(CH)2]…
 Physical Properties:
 White amorphous
powder,
 Slight bitter taste,
 Slightly soluble in
Water,
 Insoluble in Alcohol
 soluble in Glycerin
 Uses
 Antacid
 Astringent
 Fluid electrolyte
 Emulsifying agent
 Absorb carbon dioxide
 Making of glass
 White washing of cloth

32. Sodium Hydroxide [NaOH]
 Synonym: Caustic soda, soda lye
 Preparation: By treating sodium carbonate
with lime water
Na2CO3 + Ca(OH)2 = 2NaOH + CaCO3
 Storage : well closed container & protect from
moisture & CO2

33. Sodium Hydroxide [NaOH]….
 Properties :-
 White amorphous
pellets
 Slight bitter taste
 Soluble in water,
alcohol and glycerin &
 Deliquescent in nature
 Uses :-
 Alkalizing agent
 Disinfectant for animal
houses
 For preparation of soap
 Absorb CO2 gas
 Common laboratory
reagent

34. Question Bank
 Explain
– Traditional acid-base theory with examples,
– Discuss Arrhenius acid-base theory with example and list
limitations for it.
Or
– Define acid and base as per Arrhenius theory and write
drawbacks of it.
– Bronsted and Lowry acid-base theory with examples,
– Lewis acid-base theory with examples.
 Give Monograph for: all Official Acid as well as base
 Define with examples
– Strong & Weak Acid and Base
 Define and give types of Buffer Solutions